Temporarily reactivate marmalade for python

Seems that python is not a built-in package in at least
Ubuntu packages

core/contribsys.el

@@ -2,6 +2,8 @@
 (require 'package)
 (setq package-archives '(("ELPA" . "http://tromey.com/elpa/")
                          ("gnu" . "http://elpa.gnu.org/packages/")
+                         ;; temporarily reactivate marmalade because of python
+                         ("marmalade" . "http://marmalade-repo.org/packages/")
                          ("melpa" . "http://melpa.milkbox.net/packages/")))
 (package-initialize)
 (setq warning-minimum-level :error)